Is there a secret trick to sanding end grain?

Discussion in 'Luthier's Corner' started by Tcjbrown, Nov 5, 2016.

  1. I'm currently working on a Queensland Maple bass, and I'm having a devil of a time trying to sand out the end grain scratches. Is there a magical technique/satanic ritual/alien species that's really good at getting out end grain scratches?
  2. Bent77


    Mar 6, 2013

    I wrap the Emory cloth around an old toilet paper tube for inside contours as well
    Tcjbrown likes this.
  3. rudy4444


    Mar 13, 2012
    Central Illinois
    5" Random orbit sander and progressively finer grits; make sure you are completely sanded before switching the the next finer grit. Depending on wood and what you're finishing with you might be able to stop at 320.
    Tcjbrown likes this.
  4. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Use a good sharp file instead of sandpaper. The thing about sandpaper is that it is flexible, even when used on a hard block. End grain wood has hard ridges and soft valleys. When sanding with coarse paper, the abrasive grains dig down into the soft valleys and slide over the hard ridges. You sand and sand until the scratches are out of the valleys, and you end up with a washboard. So, then you try to sand down the hard ridges, and you end up cutting more deep scratches in the valleys. Repeat.

    On a file, the teeth are all held stiffly in line. When you slide it over the end grain, it trims down the hard ridges as it removes the scratches in the valleys.

    On perimeters of bodies, I do the shaping with 2nd and Smooth half-round files. Once the curves and contours are right, I go over it with a #2 Swiss half-round file to remove the last file marks from the Smooth file. Last, I go over it lightly with 220 paper on a soft rubber block. That blends the last of the facets and lines and preps the surface for the finish.

    The important thing is, after you've gotten the scratches out with the files, only sand with light pressure. Heavy pressure, even with finer grits, will scratch out the valleys again.

    If you aren't familiar with file designations, there are two series of file grades; the American Series and the Swiss Series.

    The American Series, going from coarsest to finest, are: Coarse (not seen much these days), Bastard, 2nd, and Smooth. These are the files that are most commonly used and seen in hardware stores. They are stamped Bastard, 2nd, or Smooth.

    Swiss series files are numbered starting with #00 (the coarsest), #0, #1, #2, #3, #4, #6. These are much finer files than the American series. The #0 Swiss is about equal to the American Smooth. For working hardwoods, the #2 Swiss is about as fine as you can use. #2 Swiss cuts about like 400 grit paper.

    I use #4 Swiss files for final smoothing of metal parts. It cuts about like 800 grit, almost to polishing level.

    My recommended essential files for Luthiers:
    6" Half-round Bastard, Smooth, and #2 Swiss
    8" or 10" Half-round Bastard and Smooth
    12" or 14" Half-round Bastard
    8" or 10" Round (rat tail) Bastard and Smooth
    1/8" and 1/4" round Chainsaw files
    8" Square Bastard and Smooth

    Those are the files that I use every day for woodworking.
    Last edited: Nov 5, 2016
  5. Everything @Bruce Johnson says is gospel as far as I'm concerned. :)
    Dean N and ctmullins like this.
  6. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Oh no, I don't have that kind of connections....I just have a lot of years of experience designing and building things. Messing with tools and figuring out how to make things are what I live for. He who dies with the most tools and skills, wins.
    Tcjbrown, NealBass, pudge and 5 others like this.
  7. Dean N

    Dean N

    Jul 4, 2006
    Pittsburgh, PA
    Bruce, thanks for posting and sharing what you know.

    You should write a book or something.
  8. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    I am writing a post at a time here on TB! Collect them all and print them out!
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    Primary TB Assistant

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